Most spam detection today is done by looking at an incoming message and trying to deduce whether or not it is spam based on keywords in the message. The problem with this approach is that just looking at keywords may not indicate whether or not a message is spam. Further, these approaches are rigid and cannot readily distinguish between spam, as defined by a set of keywords, and e-mail that is unwanted, unsolicited, or annoying.
In the drawings, like reference numbers generally indicate identical or similar elements. Additionally, generally, the left-most digit(s) of a reference number identifies the drawing in which the reference number first appears.